One proposed power output apparatus has a generator, an internal combustion engine, and a drive shaft that are respectively connected to a sun gear, a carrier, and a ring gear of a planetary gear mechanism, and a motor that is linked to the drive shaft. This power output apparatus distributes the output power of the internal combustion engine into the generator and the drive shaft (see, for example, Japanese Patent Laid-Open Gazette No. 2004-56922). Even when the drive shaft is to be rotated in a reverse direction in response to a driver's operation, the torque transmitted from the internal combustion engine to the drive shaft functions to rotate the drive shaft not in the reverse direction but only in a normal direction. Under the condition of a sufficient state of charge of a battery, the prior art power output apparatus stops the internal combustion engine and drives the motor to rotate the drive shaft in the reverse direction. Under the condition of an insufficient state of charge of the battery, on the other hand, this prior art power output apparatus controls the generator to generate electric power with the output power of the internal combustion engine. The motor consumes the generated electric power and outputs the sum of a cancellation torque to cancel out the output torque of the internal combustion engine for normal rotation of the drive shaft and a required torque for reverse rotation of the drive shaft. This rotates the drive shaft in the reverse direction.